The trials and tribulations of having an eco house built - and then living in it!

Wednesday, 27 July 2011

Here it comes ... (Week twenty-five)

I don't know why but this is the bit of the build I've been most excited about. On Monday the solar panel installers from Rayotec (www.rayotec.com) arrived on site and here’s one of the panels that are now on our roof.

Over 1,000 watts of energy from the Sun hits each square metre of our planet every second, which means that every hour Earth gets enough energy for a year’s worth of human usage; a statistic that, frankly, makes my brain ache. Our roof will make use of some of this energy to produce electricity and heat water. I mentioned the panels and tubes that are going on the roof a few weeks ago but now, as they say, here comes the science bit:

The solar panels make use of the “photovoltaic effect” which was discovered in 1839 by Edmond Becquerel. He noticed that some materials produce an electric current when exposed to light and this principle was explored throughout the 19th and 20th centuries by such luminaries (geddit?) as Einstein, leading to the development of things like solar powered calculators.

The roof panels look and feel like an aluminum whiteboard with an electrical connector on one side and on the surface (the blue side) they feel just as smooth but they are covered with thin layers of silicon. Depending on how it is treated silicon can either be an insulator or conductor and here it’s been ‘doped’ so it acts as a semiconductor.

When the sun shines on the panels the silicon absorbs the energy and releases electrons, creating a direct current across the layers. The stronger the sun and the greater the number of panels the more electricity you create and, as you see from the photos we have 28 panels. There’s a neat graphic of how they work from the energy savings’ trust.

By the ridge in the middle of the roof we also have the tubes for the solar thermal system. The tubes are designed a bit like a vacuum flask with two layers of glass and a vacuum between them. Under the tubes there’s a mirror, which helps maximise the amount of sun they receive and the inner tubes are treated with Aluminum nitrite which absorbs sunlight and converts it into heat energy. Full details are available on the manufacturer’s website.

So, during daylight, we ought to be self-sufficient with our electricity and on sunnier days we will be merrily farming electricity. The environmental impact of the whole system is equivalent to taking three cars off the road, which doesn’t sound like much in the great scheme of things but it’s a start. Anything we can do as individuals to reduce climate change has got to be good.